Small (SKCa) Ca2+-activated K+ channels in cultured rat hippocampal pyramidal neurones

Small (SKCa) Ca2+-activated K+ channels were identified in membrane patches excised from cultured CA1-CA3 pyramidal neurones of the neonatal rat hippocampus. When recorded in low-K+ extracellular solution ([K+]o=2.5 mM), SKCa channels had a low conductance (@3 pS at 0 mV), were activated by >/=175 nM Ca2+ (Po=0.54 at 500 nM Ca2+) and there were two open-time components (2.1 and @70 ms) to their activity. These properties of single SKCa channels are similar to those of slow after-hyperpolarization channels (sAHP) previously inferred from fluctuation analysis of the sAHP current. It is concluded that the SKCa channel reported here may be the channel that generates the sAHP in hippocampal pyramidal neurones.